[1]
An experimental study was conducted to investigate the behaviour of Ultra High Strength Self Compacting Fiber Reinforced Concrete using quartz sand and quartz powder. The investigation is done to obtain the mechanical properties of Ultra High Strength Self Compacting Fiber Reinforced Concrete (UHSSCFRC) by using the partial pozzolanic admixture, i.e. quartz powder, in addition to the use of hooked end steel fibers and complete replacement of river sand with quartz sand. In recent world, strength and flow ability in heavy reinforced structures have become a major issue. To boost up the strength, mineral admixtures like micro silica is added and the water-cement ratio has been drastically reduced. To overcome the reduction of water content, chemical admixtures are added in less dosage. The chemical admixture like superplasticizer and viscosity modifying agent increases the flow ability without segregation. Due to depletion of natural resources, we have to work at alternate fine aggregate. Hence it is required to use alternate materials like quartz sand to obtain more durability. Quartz sand has more resistance against acidic content in nature and high temperatures. The paste prepared by using quartz sand and quartz powder is much denser than the paste prepared by river sand, which easily flows in and compacts itself even in heavy reinforced structures. The study revealed that quartz powder and quartz sand can be used for developing UHSSCFRC by reducing water content and satisfy the flow properties according to EFNARC. The test result for acceptance characteristics for self compacting concrete such as slump flow, v-funnel, and L-box are presented. Further, the strength characteristics for 7 days, and 28 days are also presented.
With the growing population, there is a huge demand for infrastructure. To produce huge infrastructure, high strength concrete and heavy reinforcement are needed [2,3]. In heavy reinforcement, ordinary concrete can compact itself and need vibration [4]. So the Ultra High Strength Self Compacting Fiber Reinforced Concrete has been developed.
The Ultra High Strength Self Compacting Fiber Reinforced Concrete is developed from the combination of Self Compacting Concrete (SCC) and fiber reinforced concrete to overcome the problems like heavy reinforcement, strength, and non-availability of materials [8]. The UHSSCFRC is made by using coarse and fine aggregate, huge amount of cement, pozzolanic materials, mineral admixtures and chemical admixtures. The UHSSCFRC are affected by the characteristics of materials and the mix proportions [22]. According to Okamura and Ozawa [12], the coarse aggregate in concrete should be fixed to 50% of total aggregate content and the rest of volume is fine aggregate [4] . The water-powder ratio is drastically reduced and super plasticizers are added to increase strength and VMA to resist segregation. The dosage of S.P and VMA is from 0.5% to 2% of powder content. The required proportions are determined by conducting a number of trials [9].
In this paper, the river sand is completely replaced by quartz sand which is much durable and gives strength. The paste is prepared by cement, micro silica, and quartz sand which are the most important in SCC [14]. The quartz powder acts as both filler and pozzolanic material which makes the mix denser. The micro silica is used as the mineral admixture, to boost the strength and reduce the heat of hydration [18]. This even acts as a filler and react with cement to form a good bond. The super plasticizer is used to reduce the water content and the viscosity modifying agent is used to resist the segregation [1] . Fibers are added to improve the tensile strength [4].
This paper describes the procedure to develop UHSSCFRC. The test result for acceptance characteristics for self compacting concrete such as slump flow, v-funnel, and Lbox are presented. Further, the strength characteristics for 7days, and 28 days are also presented.
Self Compacting Concrete usually offers several high performance properties in terms of mechanical behavior and durability over Conventional Vibrated Concrete (CVC) [6, 8, 12]. These properties could even be improved by incorporating fibres in SCC, thus obtaining Fiber Reinforced Self Compacting Concrete (FRSCC) (Torrijos, et al. 2008). The fibres in concrete serves as crack arresters and contribute to an increased energy absorption compared to plain concrete [11]. Depending on parameters such as fiber volume, fiber-type, fiber geometry, fiber aspect ratio, and fiber inclusion, the concrete improves the characteristics such as tensile strength, compressive strength, elastic modulus, crack resistance, durability, fatigue strength, resistance to impact and abrasion, shrinkage, expansion, thermal characteristics and fire resistance to different extent [27]. The steel fiber is the most common fiber type in the construction industry; plastic, glass and carbon fibres contribute in some quantity to the construction industry.
Quartz is the second most common mineral in the earth's continental crust. Its IUPAC name is silicon dioxide, and the chemical formula is SiO . Mostly, quartz consists of 93% to 96% of silica. In this paper, the quartz powder and quartz sand are the products of quartz. Mostly quartz is used as a filler material, but it is slightly pozzolanic [21] . As quartz is chemically made of one atom of silica and two atoms of oxygen, the bond formed is covalent and stable, which makes it inert [10]. But the amorphous silica reacts with the alkaline substances present in concrete produced as the product of hydration [13].
The calcium hydroxide produced at the time of hydration is the waste product in concrete [7]. The quartz powder reacts with calcium hydroxide and produces a gel [15] . The gel produced acts as a binding material and due the chemical reaction, a good bond is formed and the strength is increased [20]. The gel formed makes the concrete denser so it easily flows in the heavy reinforced structure [19].
The CaSiO3 + H2O is the gel formed. The finer quartz sand and quartz powder particles fill the gap between the coarse aggregate, this in turn increases the strength of concrete. Since the quartz sand is slightly acidic in nature, it is more durable than river sand.
Ordinary Portland cement of 53 grade available in the local market is used in the investigation. The cement used has been tested for various proportions as per IS 4031-1988 [21] is found to be confirming to various specifications of IS 12269-1987 [23]. The specific gravity was 3.1 and fineness was 2800 cm2/gm.
The Micro Silica used in the investigation was procured from the local market. The oxide composition of micro silica has been listed in Table 1.
Table 1. Typical Oxide Composition of Micro Silica
Quartz powder is in the order of 300 mesh. The specific gravity of Quartz powder is 2.635. Table 2 enlists the properties of Quarts powder.
Table 2. Properties of Quartz Powder
The coarse aggregate used is granite coarse aggregate [24, 25]. The size varies from 4.75-10 mm (Table 3).
Table 3. Physical Properties of Coarse Aggregate
Quartz has a hardness of 7 on the Mohs scale. The size of quartz sand is 0.3 to 0.8 mm, and the specific gravity of sand is 2.46. This comes under Zone – II specification (Table 4).
Table 4. Properties of Quartz Sand
Super plasticizer namely Glenium B233 and VMA namely Glenium Stream 2 are used [16]. The normal dosage of Glenium B233 is between 0.5 to 2% of powder content (Cementation material) (Table 5). Glenium Stream 2 is dosed at the rate of 0.1 % to1.8% of the cementation material.
Table 5. Properties of Super Plasticizers
Hooked steel fibers as shown in Figure 1 consist of hard drawn carbon steel wire [1]. Fibres are hooked at each end to give improved mechanical anchorage of the fibers within the concrete. The length is 30 mm and diameter is 0.5 mm with aspect ratio of 75, which is used through the project. The fibers slightly increases the compressive strength, but have much effect on increase in flexural and split tensile strengths [26].
Figure 1. Hooked end Steel Fibers
Self-consolidation concrete mix is made using 680 kg/m3 of OPC 53 grade cement, 102 kg/m3 of micro silica and quartz powder is varying at 68 kg/m3 of mix 1, 102 kg/m3 of mix 2, 136 kg/m3 of mix 3, 170 kg/m3 of mix 4, 204 kg/m3 of mix 5, and 238 kg/m3 of mix 6. 1.5% of cementation material is used as super plasticizer and 0.25% of cementation material is used as viscosity modifying agent [17]. Fibers are tuned to 1.5% of cementations material (Table 6).
Table 6. Mix Proportions
The concrete mixtures used in this study were laboratory produced with a pan mixer of 80 litre in capacity. Buttering of the mixer (disposal of the first mix) was always firstly conducted before the first intended batch. This is to eliminate the effect of the mixer dryness/wetness condition.
The following mixing procedure was followed for all HSSCC mixtures. Firstly, the total content of fine aggregate and course aggregate were dry mixed altogether in the mixer for 2 min. Then cementitious materials (cement + micro silica + quartz powder) are added and mixed thoroughly. Secondly, water and chemical admixtures like sp and VMA are premixed in a beaker and stirred thoroughly. The premixed liquid (Water+SP+VMA) was added and the mixing was continued for further 2 min. At last, the fibers were added and mixed thoroughly for 3 min until uniform mix is obtained. Once the mixing time was complete, the rheological tests (slump flow test, v-funnel test and L-box test) were performed in quick succession. The buttered steel moulds were then placed horizontally on the floor, and were filled in a single layer. HSSCC was placed under its own weight without compaction. Immediately after casting, the top surface of the specimens was leveled. Then, all specimens were stored in laboratory atmosphere until de-molding. The moulds were removed after 24 h and all specimens were cured in water until testing.
Figure 2. Flow Table
Figure 3. V Funnel
Figure 4. Compressive Strength
Figure 5. Split Tensile Strength
Figure 6. Flexural Strength
The flow table and V-funnel analysis is shown in Figures 2 and 3 respectively. Figures 4, 5 and 6 show the compressive strength, Split tensile strength and Flexural strength respectively for 7 and 28 days. Based on the experimental studies carried, the following conclusions can be drawn:
Table 7. Flow Characteristics
Table 8. Strength Characteristics